1. Field of the Invention
The present invention relates to a laser apparatus capable of emitting laser beams of a plurality of different wavelengths.
2. Description of Related Art
As a laser apparatus capable of emitting laser beams of a plurality of different wavelengths, there have been known apparatuses using an argon dye laser capable of changing wavelengths of laser beams to be emitted, a krypton laser capable of emitting laser beams of multiple wavelengths, or others. Those lasers have been used in various fields including a medical field; for example, in ophthalmic surgical operations using laser beams of different wavelengths according to affected parts or treatment purposes. For instance, in the ophthalmic surgical operations, treatments on different diseases (affected parts) are performed by using laser beams having wavelengths (colors) centered in the visible region. In some disease cases, the laser beams of different wavelengths, for example, red, green, and other color beams, are irradiated simultaneously or selectively. It is therefore convenient if a single apparatus can emit laser beams of a plurality of different wavelengths.
The aforementioned laser apparatus capable of changing wavelengths of laser beams is concretely an apparatus using a gas laser or a dye laser. These lasers have many problems in a short life of a laser tube, a need for a large amount of electric power, an increased size of the apparatus, etc. Instead thereof, therefore, a laser apparatus capable of emitting (oscillating) laser beams of multiple wavelengths with use of a solid-state laser has been studied. Under those circumstances, as disclosed in Japanese patent unexamined publication No. 10-65238, there has been proposed a method of emitting laser beams of plural various wavelengths by changing output mirrors also used as resonant mirrors on a resonation optical axis.
In relation to the method of changing the output mirrors also serving as resonant mirrors, the apparatus which generates laser beams of multiple wavelengths by oscillating second harmonic light requires replacement of nonlinear crystals, output mirrors, and others used for producing the second harmonic light, increasing the number of optical components. This also causes the difficulty in ensuring the alignment accuracy of the individual optical components during resonance.
In other words, the resonant mirror usually has a curved portion. If angle deviation of the mirror is caused by the replacement, the output efficiency of a laser beam is deteriorated (the output power is reduced). If angle deviation of the nonlinear crystal is caused by the replacement, the output efficiency is similarly deteriorated. In addition, the nonlinear crystal needs to be controlled in relation to the temperature, so that a temperature control unit such as a Peltier element or the like has to be moved together with the nonlinear crystal.
The present invention has been made in view of the above circumstances and has an object to overcome the above problems and to provide a laser apparatus capable of efficiently emitting laser beams of plural various wavelengths while easily ensuring the accuracy of alignment of the optical component in changing the wavelengths of laser beams.
Additional objects and advantages of the invention will be set forth in part in the description which follows and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
To achieve the purpose of the invention, there is provided a laser apparatus capable of emitting laser beams of a plurality of different wavelengths, the apparatus including: an exciting light source; a solid-state laser medium which emits light of a plurality of peak wavelengths by light from the exciting light source; a first resonance optical system including a first resonant mirror and a second resonant mirror placed with the laser medium sandwiched between them to resonate light of a first peak wavelength among the plurality of peak wavelengths emitted from the laser medium, and a first wavelength converting element located between the laser medium and the second mirror to oscillate second harmonic light of the first peak wavelength light as a first laser beam; a movable reflection mirror disposed changeably between a first position and a second position with respect to an optical path between the laser medium and the first wavelength converting element so that, when the reflection mirror is disposed in the first position, it constitutes the first resonance optical system; and a second resonance optical system including a third resonant mirror which resonates light of a second peak wavelength emitted from the laser medium in cooperation with the first mirror via the movable mirror disposed in the second position, the light of the second peak wavelength being different in wavelength from the first peak wavelength, and a second wavelength converting element located between the third mirror and the movable mirror disposed in the second position to oscillate second harmonic light of the second peak wavelength light as a second laser beam.
According to another aspect of the present invention, there is provided a laser apparatus capable of emitting laser beams of a plurality of different wavelengths, the apparatus including: an exciting light source; a solid-state laser medium which emits light of a plurality of peak wavelengths by light from the exciting light source; a first resonance optical system including a first resonant mirror and a second resonant mirror placed with the laser medium sandwiched between them to resonate light of a first peak wavelength among the plurality of peak wavelengths emitted from the laser medium and a first wavelength converting element located between the laser medium and the second mirror to oscillate second harmonic light of the first peak wavelength light as a first laser beam; a movable reflection mirror movable onto/off from an optical path between the laser medium and the first wavelength converting element; and a second resonance optical system including a third resonant mirror which resonates light of a second peak wavelength emitted from the laser medium in cooperation with the first mirror via the movable mirror moved onto the optical path, the light of the second peak wavelength being different in wavelength from the first peak wavelength, and a second wavelength converting element located between the third mirror and the movable mirror moved onto the optical path to oscillate second harmonic light of the second peak wavelength light as a second laser beam.